Feasibility and Economic Analysis for Creating a Viable Cogeneration Design for the Campus Wood-Fired Boiler

Abstract. Although combined heat and power (CHP) generation is more efficient that just operating a boiler for heat alone, there are many technical and economic challenges to be addressed before a successful conversion of the existing boiler to a CHP. The University of Idaho has operated a central heating plant for over 100 years. The Steam Plant utilizes fuel oil, coal, natural gas, and wood chips in its four steam boilers. Presently, wood chips comprise the primary fuel for the facility‘s large wood fired boiler, and natural gas supplies backup heat via a gas fired boiler during times of high steam demand. Boiler pressure and flow output vary to meet campus demand, but system pressure is typically set at about 135 psig. There is currently no electrical cogeneration integrated in the boiler system. Performance, and economic implications regarding the ability of different configurations of a steam-drive turbine and generator to produce power as a byproduct of meeting campus heating and cooling demand served as motivation for this case study project. This paper analyzes different system architecture, additional fuel requirements, system efficiencies, electrical generation capacity, utility interconnections, and cost-benefit analysis of each configuration. The study concluded that the University of Idaho could save $190,000/year with an implementation cost of $1.5 M. (Smith, 2014)